The present invention is directed generally to circuit monitoring devices, and more particularly, to an improved hot line indicator.
Various devices have been developed for testing for the presence of high voltage on electrical conductors in power distribution systems to reduce the hazard of working on or near such systems.
One such early device was an electroscope wherein a pivoted vane was arranged to be repelled from a fixed vane on contact with an energized line. This device had to be positioned very precisely since the force of electrostatic repulsion of the vanes was relatively small and opposed by gravity. Another early device utilized an incandescent lamp in conjunction with a high resistance series resistor to ground. This device was cumbersome, could not detect small charges or high voltages through a high impedance, and required an ohmic ground connection. Later versions of this device which substituted a meter for the lamp were also unsatisfactory.
More recently, neon glow lamp devices, popularly called statiscopes, have come to be employed as voltage detectors. The neon lamp used in such statiscopes unfortunately provides a dim indication of voltage which is difficult to see from the end of a lineman's hot stick.
The present invention overcomes these drawbacks by providing a hot line indicator which incorporates a high impedance non-mechanical visual display device in the form of a liquid crystal display. This results in an indicator of increased sensitivity which is more compact and easier to manufacture, does not require an external ohmic connection to ground and which provides a large non-ambiguous indication to the user as to whether a monitored line is powered.
Accordingly, it is a general object of the present invention to provide a new and improved hot line indicator.
It is a more specific object of the present invention to provide a hot line indicator which avoids the use of electromechanical indicator mechanisms.
It is a still more specific object of the invention to provide a hot line indicator which is more compact and easier to manufacture.